Chalcogenide–gold dual-layers coupled to gold nanoparticles for reconfigurable perfect absorption. Issue 43 (21st August 2019)

• Record Type: Journal Article
• Authors: Cao, Tun; Liu, Kuan; Lu, Li; Chui, Hsiang-Chen; Simpson, Robert E.
• Is Part Of: Nanoscale. Volume 11:Issue 43(2019)
• Page Start: 20546
• Page End: 20553
• Publication Date: 2019-08-21
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c9nr04759j
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : We demonstrate Au nanoparticles coupled to a gold/chalcogenide dual-layer absorber, exhibiting angle and polarisation-independent high absorptance. Abstract : Recently, tunable high absorptance from various nanophotonic structures has been demonstrated. However, most of these structures require nano-lithography, which is expensive and slow. Lithography-free tuneable absorbers are rarely explored for tuneable visible and near-infrared photonics. Herein, we demonstrate a gold (Au)/chalcogenide dual-layer that is resonantly coupled to Au nanoparticles (NPs). The structure exhibits angle and polarisation-independent high absorptance. At resonance, waveguide cavity-like modes are excited between the film and NPs whilst gap plasmon modes are excited between the NPs. Coalescence of the waveguide cavity-like modes, the gap plasmon modes, and the highly absorbing chalcogenide semiconductor not only leads to perfect absorptance but also a reconfigurable response via reversible structural phase transitions in the chalcogenide film. In the amorphous state, the design provides nearly perfect absorptance for both p- and s-polarisation states at an incident angle of 20°. However, after switching to the crystalline state, the peak absorptance spectrally broadens and redshifts from 980 to 1520 nm. This experimental observation was theoretically validated by the finite element method. Thermal-electric modeling was performed to show that the structural transition from crystalline to amorphous states is possible in just 5 ns, thus allowing high-speed reconfigurable perfect absorbers.